Some SiteGround web hosting plans have a Staging feature in cPanel. It's a very handy feature, but there's an idiosyncrasy that has one specific effect in Beaver Builder.
In a SiteGround staging site, the WordPress address URL and site address URL in Settings > General are not changed to point to the staging site. Beaver Builder and Beaver Themer plugin code is written in such a way that this URL mismatch only causes a problem when new images are added to the staging site in a Slideshow module or as a Slideshow row background. These URLs cause Beaver Builder to look to the main site for images, but it doesn't find the new ones because they haven't been added there yet.
The good news is that it's only on the staging site that you can't see new images in a slideshow. Once you push your staging site live, the images you added to the Media Library will appear, since the new images are now copied over to your main site. Also, this issue applies only to the Slideshow module and row background, not to the Content Slider or any other module or type of row background image.
SiteGround has agreed to implement a workaround for this problem in their Staging code. In the meantime, if you need to see newly added slideshow images on your SiteGround staging site, you can add the following line to the wp- config.php file in the staging location and substitute the correct staging site URL, and then remove it before you push the changes back to your main site.
Replace the staging number and domain in the URL with the correct one for your staging site.
Where can you find the wp-config.php file? SiteGround staging sites are located in your home directory in the staging folder. For example, if your staging URL shows 'staging13' as the subdomain, then the location is /staging/13.